<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>createClass 创建子类</title>
</head>
<body>
  <canvas id="canvasBox" width="600" height="600" style="border: 1px solid #ccc;"></canvas>

  <script src="../../script/fabric.js"></script>
  <script>
    // 创建画布
    let canvas = new fabric.Canvas('canvasBox')

    // 半圆子类
    let Semicircle = fabric.util.createClass(fabric.Object, {
      initialize(options) {
        this.callSuper('initialize', options)
        this.width = 100
        this.height = 50
      },
      _render(ctx) {
        ctx.fillStyle = this.fill || '#333'
        ctx.lineWidth = this.strokeWidth || 1
        ctx.strokeStyle = this.stroke || '#333'
        ctx.beginPath()
        ctx.arc(0, -25, 50, 0, 180 * Math.PI / 180)
        ctx.closePath()
        ctx.stroke()
        ctx.fill()
      }
    })

    // 半圆
    let semicircle = new Semicircle({
      top: 100,
      left: 100,
      stroke: 'pink',
      fill: 'yellowgreen',
      strokeWidth: 10
    })

    canvas.add(semicircle)
  </script>
</body>
</html>